Power vehicles for carrying out diverse tasks are known. For instance, power lawn mowers are well known for use in turf and lawn maintenance. Such mowers may range from small, walk-behind mowers such as those used by homeowners, to professional grade riding mowers adept at mowing larger areas. While embodiments of the present invention may be directed to control systems for use with a wide variety of power vehicles, it will, for the sake of brevity, be described with respect to power riding or walk-behind mowers.
Power mowers typically incorporate a prime mover (e.g., internal combustion engine) and a variable, e.g., hydraulic, drive system. The drive system may include left and right hydraulic motors coupled to left and right drive wheels, respectively. Power may be transmitted from the prime mover to the left and right hydraulic motors, e.g., via one or more pumps, to drive the left and right drive wheels independently. The rotational speed and direction of each drive wheel may then be controlled by associated drive control levers manipulated by an operator. By manipulating the control levers independently, each drive wheel can be separately driven forward or backwards at varying speeds. Thus, the mower may be propelled forwardly or in reverse. By powering one wheel in the forward direction and slowing, stopping, or powering the opposite wheel in the reverse direction, the mower can execute a turn.
With many conventional mowers, the engine and hydraulic pumps are attached to a frame of the mower, while the cutting deck is adjustably positionable at varying elevations relative to the frame to provide for different cutting heights. While effective, moving the cutting deck relative to the engine does have drawbacks. For example, with a belt-powered cutting deck, it is desirable to ensure that the fleeting angle (the belt angle formed between the engine driving sheave and the driven sheave(s) of the cutting deck) is maintained within an acceptable range as the deck moves up and down to minimize belt separation and/or wear. Depending on the distance between the engine and deck, the range of acceptable fleeting angles may be limited.
Another issue with some mowers concerns positioning of the drive control levers. For instance, each drive control lever may generally be positioned between a neutral and a full forward (and a full reverse) position. The levers are generally sized and configured so that the operator may manipulate the levers over their normal range of motion (e.g., from neutral to full forward) without relocating his or her hands. In the full forward position, the levers may be configured to rest against stationary stop bars. Such a configuration permits the operator to hold the levers against a fixed stop during normal operation, reducing potential fatigue in the hands, wrists, and arms. The fixed stop may also provide a degree of lever stability, minimizing inadvertent lever movement as a result of vehicle motion.
While effective, this full forward position may result in a vehicle speed in excess of what is desired for some mowing tasks. To reduce the speed, the operator may back the control levers off from the full forward position. Unfortunately, this technique may prevent the operator from resting the levers against the fixed stops. Alternatively, the engine throttle may be reduced. While throttle reduction is effective at reducing maximum vehicle speed, it also reduces the rotational speed of any attached implements, e.g., the blades of the cutting deck. As a result, cutting efficiency of the mower may be reduced.